Eh, I wouldn't assume the dog can/should go to someone else with a disability. Many service dogs in the US are owner trained to help very specific conditions/symptom combinations, and even two people with the same disability might have vastly different needs in a service dog. And it's entirely possible the the dog isn't a service dog, but an ESA or even therapy animal. Or she performs a service at home, but isn't public access trained. Or isn't working out as a service dog at all, which is why the current owners are looking to rehome (failed service dogs can be great pets, of course, but this is a possibility I'd consider with such a young service dog being rehomed). Of course if she's a program dog they need to abide by that program's contract re: rehoming, but many many US service dogs aren't connected to any program.
Rytry, without knowing these people or this dog well, I'd just look at this like you're thinking of taking on a dog that has some training and probably good house manners/potty manners, but the rest is a bit of an unknown. Shepherds can be wonderful family dogs, and I would expect a dog that has been fully and successfully trained as a SD, including public access, and has been working successfully to be very stable and comfortable in new situations, but some shepherds can be more on the nervy and sensitive side. Because you don't know for sure what kind of work this dog's been doing and how well she does it, it's really hard to make assumptions about where her personality might fall. Treat it like any adoption/rehome: ask questions. You don't need to pry about their disability, of course! Just ask about her general behavior and personality, maybe take a walk with her and them (or offer to take her yourself) so you can see how she does outside (usually a more exciting and less predictable environment for dogs, though it depends on the area of course), have her meet your kids in a park or other neutral space, etc. to get a better idea about her, personally.
She may or may not be a dog who needs a 'job', but dog jobs don't need to be one specific thing (being a service dog, in this case). It might be training for a sport, walking/hiking with a safe weighted backpack, or just learning fun tricks so they can do things around the house like finding objects you ask for, picking up trash, grabbing dirty laundry to hand you, fetching your kids when you ask, etc! She may have a head start on that last part - these kinds of behaviors are frequently used as service dog tasks, though of course it depends on the needs of the handler.